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Ameron Water Transmission Group completes “Pipeline Project of the Year”
The Ameron International Corporation’s Water Transmission Group received the Steel Tank Institute-Steel Plate Fabricators Association’s 2009 Pipeline Project of the Year Award. The 144-inch inside diameter Arrowhead Tunnel Project, which for more than a decade, was subject to delays due to extremely difficult tunneling and ground water conditions, was completed in late 2009.
The Arrowhead Tunnel System which is now in service is capable of doubling the water delivery capacity (up to 650 mg/d) from the east branch of the California State Aqueduct to Southern California (the Colorado River Aqueduct and Diamond Valley Lake), bringing much needed water to a part of the state where it has historically been in short supply.
Specified as a two-pass tunnel lining system, the project called for a dual containment tunnel lining structure with the annular space between the two liners grouted with cement mortar. The initial outer liner is a precast reinforced concrete segmental tunnel designed to withstand all ground loads and water infiltration during construction.
For the final inner liner, Ameron manufactured a rigid-wall composite steel and concrete pipe that was designed to withstand external heads of up to 1,200 feet (520 psi), a maximum internal pressure of 80 psi and tunnel depths that ranged from 800 to 1,590 feet beneath the San Bernardino Mountains. Since the tunnel system is constructed in the middle of several fault lines, the design criteria required the 144-inch diameter tunnel liners to survive an earthquake of up to 8.0 magnitudes. It is believed that this project is unique due to its large 12-foot diameter and exposure to 1,200 feet of external pressure.
Before a single pipe section of the rigid-wall composite steel and concrete tunnel liner was installed, Ameron worked closely with the Metropolitan Water District’s engineers and conducted more than eight months of critical testing and analysis, which included: